Vol 57, No 2 (2016)

Sorption of copper ions from model solutions (1–100 mg/dm³ Cu) at pH = 5.5–9.5 and from wastewater (of the composition, mg/dm³: 0.2–0.4 Cu, 0.2–0.3 Zn, 0.3–0.4 Ni, 0.3–0.5 Fe, 0.6–0.9 Pb, 1.8 As, 0.2 Mn, 3.2 Mg) at pH = 8.5 on modified montmorillonite of the Zyryanovskoe deposit in the Naform is investigated in comparison with the known liming method. The considerable sorption capacity of highly dispersed alumosilicates (~3.0 mg-eq/g) makes it possible to acquire a precipitate with a high content of ions of heavy nonferrous metals from the precipitate and purified water with residual concentrations of metals (Cu < 0.01 mg/dm³) corresponding to discharge norms into the surrounding medium.

A novel process was developed to improve the extraction of valuable metals from a manganese-bearing gold-silver ore. Before cyanidation, a reductive sulfating leaching pretreatment process was adopted to preferentially dissolve manganese from the primary ores, according to mineralogy of the ores and possible leaching thermodynamic calculations of manganese minerals, and iron scrap was firstly introduced as reductant because of its low cost and wide source in China. In pretreatment tests, the effects of iron scrap concentration, sulfuric acid concentration and leaching temperature were studied, and the results indicated that manganese could be rapidly leached out to a complete degree even at room temperature. Then the reduced residue was suggested to the cyanidation process for silver and gold extraction, and the effect of cyanide concentration was also addressed. Based on the above study, pilot tests were finally conducted in Beiya 50 t/d concentrator to correctly evaluate the whole leaching process in the case of continuous production, and the gold and silver extractions in the novel process were up to 92.16 and 82.33%, respectively, corresponding to an increase of 9.08 and 45.97% compared to those in the direct cyanidation process, which are of great implications for future commercial operations of these refractory manganese-bearing gold-silver ores.

A computer analysis of the deformation mode of a billet and tool in the axially symmetric statement at the stage of established drawing of the PtNi alloy of the equiatomic composition is performed by the finite-element method in the DEFORM-2D program medium. The geometry of the diamond tool providing a decrease in rigidity and weight without varying the basic parameters of the production process is proposed.

The experimental-and-theoretical method of determining residual stresses in strip metal wares made of zirconium alloys, which manifest the transversal-isotropic properties after cold rolling, is investigated. The results show that considerable transverse and longitudinal residual stresses appear on the strip surface. The character of their distribution agrees qualitatively with the known regularities of the distribution of these quantities during rolling.

Types and fabrication methods of discretely reinforced alumomatrix composite materials (AMCMs), the wide application of which is hindered by a whole series of unresolved problems, are reviewed. These problems are the high cost of both reinforcing materials and the entire production process of composites; a not always sufficient level of strength properties, especially at elevated temperatures; the distribution nonuniformity of reinforcing particles over the volume of the aluminum matrix; and insufficient bond strength with it. It is discussed what contribution can be introduced into the solution of these problems by applying in situ processes, particularly, the SHS process, in order to fabricate cast nanostructured AMCMs. This is shown in more detail by the concrete example of the Al–10%TiC composite discretely reinforced by nanodimensional titanium carbide particles.

The influence of the remelting temperature on the structural heredity of the alloy fabricated by centrifugal SHS metallurgy is investigated. It is shown by the example of the highly boron-alloyed NiAl-based alloy that overheating the alloy by more than 100°C (above T_m) during vacuum-induction remelting leads to substantial coarsening of the components of the SHS alloy and liquation appearance. All the samples of the alloy under study had a compositional structure consisting of the matrix of the NiAl-based substitutional solid solution, network inclusions of τ-boride (Ni₂₀Al₃B₆), and dispersion inclusions of (Mo, Cr)B complex boride.

The results of analyzing the influence of operational parameters of the ejection nozzle on the characteristics of highly dispersed aluminum powder in production conditions at OOO SUAL-PM are presented. Measurements of dispersed characteristics of the spray when spraying the aluminum melt by the ejection nozzle are performed when varying the consumption and temperature of spraying gas in ranges of 0.17–0.21 m³/s and 873–933 K, respectively, as well as the melt temperature in limits of 1153–1253 K. The results of determining the median diameter of the particles (d_m) and content of the highly dispersed fraction (z) (with a particle diameter no larger than 10 μm) in the spray are presented. It is shown that, when modifying the operation parameter of the nozzle, the value of d_m decreases by 3.7–12.4%, while the magnitude of z increases by 0.4–3.2%. It is established that an increase in temperature of spraying gas affects the powder properties most effectively.

The influence of nanodimensional carbon additives on the structural-phase state and properties of sintered alloys on copper, iron, and tungsten–cobalt bases is considered. It is shown that the undissolved part of the nanodimensional additive can serve as additional nucleation centers of crystals during liquid-phase sintering and crystallization of powder compositions, which promotes structure refining. It is established that the nanodimensional diamond–graphite additive in alloys able to form solid solutions with carbon or strengthening carbide phases leads to an increase in hardness of sintered composites and an improvement in their tribotechnical properties.

The influence of alloying titanium carbonitride TiC_0.5N_0.5 by transition metals of Groups IV–VI on the mechanism of contact interaction with the nickel melt is studied. It is established that alloying metals exert a strongly destabilizing influence on titanium carbonitride TiC_0.5N_0.5, simultaneously increasing both its dissolution rate in nickel and the degree of process incongruence (the preferential transition of alloying metal and carbon into the melt). The influence of alloying on the phase stability of titanium carbonitride TiC_0.5N_0.5 in contact with a nickel melt manifests itself in its dehomogenization or phase separation. The destabilizing effect of alloying additives enhances in a series Me^IV–Me^V–Me^VI parallel with a decrease in their nitrogen affinity.

The article is a continuation of the publication cycle of the authors the on the theme “Multifunctional Protective Coatings for Especially Thermally Loaded Elements of Constructions of Hypersonic Systems.” Modern domestic approaches to the formation of single-layer and multilayered high-temperature protective coatings of various classes such as glass–ceramics ones obtained by various methods, coatings based on oxide ceramics, oxygen-free reaction-coupled coatings, and microcomposition coatings of the synergetic type are analyzed. Attention is paid to the fact that the scientific-and-applied investigation directed at the development of the structural and physicochemical models of the coating architecture and substantiation of their functioning with high-speed gas streams are almost absent. The selection of the chemical composition of coatings and production procedures of their formation is performed mainly based on the empirical basis. A series of coatings claimed as workable in conditions in a medium of tranquil or weakly perturbed air up to temperatures of 1600–2000°C is presented; however, their protective ability in conditions of the effect of high-enthalpy supersonic and hypersonic gas streams cannot be judged because of the insufficiency or absence of required data. Microcompositional coatings of the synergetic type based on the Si–TiSi₂–MoSi₂–B–Y system, which were developed in terms of an original conceptual approach to the formation of a multilevel system of heat protection of thermally stressed constructional elements made of heat-resistant materials of hypersonic aircrafts and their propulsion systems, are especially emphasized. A detailed analysis of their functioning in the composition of a unique construction wall with protected carbonaceous materials will make it possible to determine the tendencies and directions of subsequent investigations by the authors with the purpose of improving the developments.